When there is relative movement between an observer and a wave source the observed frequency changes by an amount depending on the relative velocity. This is the doppler effect, and it has been realized for a number of years that it might be the means of measuring the speed of an aircraft over the ground, using radio waves transmitted obliquely and received again at the aircraft after being scattered at the surface of the Earth. By 1937 radio techniques had developed so far that letters patent were granted for systems which then appeared to be practical. A number of severe problems remained, however, and not until the close of the war did development programmes to resolve these problems make headway. Since that time equipments have been successfully produced, both here and in the United States of America, and sufficient operational experience has been gained for the value of the process as an aid to navigation to be assessed.

When considering the navigational performance of doppler systems it is not sufficient to examine only the inherent capability of the radar system, since the overall navigational accuracy achieved is a product of the complete ensemble—the doppler, the aircraft, its pilot, the heading reference, instrument transmission linkages, and so on.

The continuous data (groundspeed and drift angle) given to high accuracy by airborne doppler equipments, could be adapted for handling by automatic computers which, accepting certain other inputs, can be designed to extract a great variety of information. This paper attempts to outline the contribution that such computers could make to long-range civil air navigation.

Those familiar with the history of navigation aids may, with good reason, be reluctant to look upon any new aid as a panacea, but there appears to be no doubt that doppler will effect a revolutionary improvement in air navigation as we know it today. We have, for the first time, an aid self-contained in the aeroplane, independent of propagation conditions or weather, capable of giving position information anywhere over the globe with an accuracy certainly adequate to join the approach facilities at the destination aerodrome. Some of us not actively engaged in flying the world's routes tend to be influenced in our outlook by the navigation problems and facilities in high-density areas like western Europe, the United States or even the North Atlantic, and we are inclined to forget that this is only a very small part of the world route structure. The intensity of aviation activity in these high-density areas warrants the establishment of a network of radio beacons, ranges, VOR's and space pattern systems like Loran and Decca to bring order into the traffic flow, besides assisting the navigation of individual aeroplanes. When, however, we consider the immense distances flown by aircraft through Africa and India to the Far East and Australia, to South America and across the Pacific, to say nothing of Communist Asia, we begin to realize what a real dearth of navigation facilities there is over the globe.

For the efficient use of doppler techniques it is necessary that the beam of short radio waves, emitted from the aircraft shall be reflected from the roughness of the surface or from a plane surface at right angles to the incident beam. Over land there are plenty of roughnesses from which the beam is always thrown back, but over smooth sea there would seem to be no surface feature which can reflect the beam. It therefore is of interest to know the effect of surface winds in producing waves and ripples with various slopes and secondly the frequency with which light winds occur in various parts of the world.

New ideas of a really fundamental character are always received with horror and alarm by the general public, and are vigorously repudiated. When Fred Hoyle, in a brilliant series of broadcasts, remarked that his physico-mathematical calculations indicated that newly created hydrogen was being continuously injected into the Universe, the B.B.C. had to take hasty countermeasures. A well-known authoress of detective stories and religious pl ys, followed by a respected professor of science, declared on the air that the earlier t lks had been merely speculative. A similar role was filled in 1543 by the theologian Andreas Osiander, who added a Preface to Copernicus's startling book De Revolutionibus Orbium Coelestium (the author having just died), to the effect that he had only intended as a mathematical hypothesis, not as a matter of fact, to picture a rotating globe revolving round the Sun. From the point of view of pure geometry it was, it is true, merely a matter of a change of coordinates. People settled back comfortably for another sixty or seventy years, until Galileo made certain awkward observations with his new telescope.

In relative plotting the movement of the observer's ship is ignored. The first bearing B1 and distance a1 are laid off from a chosen origin and after a determined time-interval the second bearing B2 and distance a2 are plotted from the same point. By connecting these two points the relative course of the observed ship is obtained, which enables the observer to tell whether the other ship will cross ahead or astern, what her distance off will be, and when the intersection will occur.

Errors in the derived aspect, in course and speed of another vessel, or in the nearest approach, found by plotting radar ranges and bearings on a relative plot can arise in a number of ways, such as errors:

(1) in the bearing as read from the PPI

(2) in range as read from the PPI

(3) in plotting the points on the plotting sheet

(4) in estimating own vessel's course and distance run during the plotting interval

(5) in timing the plotting interval

(6) ‘blunders’.

When I heard about the idea to sail a replica of the Pilgrim Fathers' Mayflower from England to America, I liked the notion. It was not my idea and I had nothing to do with the promotion. What I did was to volunteer to find a British crew and sail the ship, when she was ready—to get her across the Western Ocean, the way the original ship had gone over three and a half centuries ago. I have listened to a good many pessimists who have alleged that sailormen were dead and gone in Britain today, who declared mournfully that nobody could be found to sail ocean-going square-rigged ships in this country, and averred that, in any event, no one could possibly have the least idea how to handle a museum-piece come to life, and so on and so forth, ad nauseam.

If you want to ride up a hill on a bicycle you zig-zag up it, because although you travel a longer distance you go much faster and get to the top quicker. There is some similarity between what the cyclist does and what you are trying to achieve when you are planning for a long ocean race. Your object is to find the fastest way from the start to the finish, and whether this is also the shortest way depends on a number of imponderables such as the weather you can expect, the ocean currents, and so on. On a long race, generally the shortest way is not the quickest. What you are interested in is time, and like the cyclist, in distance only so far as it affects time. What you have got to do is to use all the elements that make you go fast, and these include not only winds and currents, but also factors such as the sailing qualities of your boat in different conditions. In addition of course you have to consider how you will stand relative to the others, not only if what you expect happens, but also if it doesn't. In other words your strategy will be tempered by some estimate of the reliability of the predictions of wind directions and currents you are working on. Your overall plan, then, is likely to be partly geographical, which is concerned with finding the least-time route; and partly strategic, which is concerned with not getting caught out.

The Russian Sputnik travels rather faster than the Mayflower or even a transatlantic racing yacht, and the launching of this artificial satellite is truly a wonderful achievement. I want to tell you why I think so, and what it means for the future.

The satellite, which was launched on 3 October, has already made 300 revolutions about the Earth. Its speed is about 17,000 miles/hour, which is about 280 miles a minute, and it makes one revolution about the Earth in 96 minutes—that is, 15 revolutions a day. Its track is inclined to the equator at an angle of about 65 degrees, so that at one time it goes up to the Arctic Circle, and at the other end of its path down to the Antarctic.

The information contained in this paper is intended to show the reliance which a pilot or air navigator can put on his expected winds in different parts of the world, in different seasons and at different heights. From the outset it must be realized that the figures given are subjective, and, in some regions at any rate, may need modification as facilities for obtaining upper air information are improved. However, it is not thought that such modification would be great and it would certainly not alter the broad pattern which is shown in the data presented here.

Australia's place in Navigation is due, in several aspects, to her geographical environment. Her first discovery is still a navigational mystery, and her first appearance on world charts about 1530 was confused by thepolitical division of longitude between Spain and Portugal. To people in the western hemisphere the most famous names in navigation are those of Columbus, da Gama, Magellan and Drake. These men were all aiming at the rich trades of the Spice Islands, whether they made for the West Indies, the Cape of Good Hope, Magellan's Straits, or the North-West Passage. They were followed by a stream of men who preferred the well-known tracks to any leading into the trackless wastes and barren coasts or Australia.

For many generations mariners have been taught the law of storms and the rules for avoiding their centres. This paper describes some of the practical difficulties of avoiding hurricanes in the south-west Pacific area, and the failure of meteorologists to appreciate the dangers and difficulties of the mariners.

About half the tropical storms observed conform roughly to the parabolic track of the law of storms. They form about 10° South of the equator during the north-west monsoon, (from December to April), and travel west-south-west, south-west and south-south-west as they gather strength and speed to a maximum; at 20° South they pause, recurve through south-south-east and south-east as they diminish in force and pass out of our consideration at 30° South.

The publication of Captain Flego's tables, which are of some theoretical interest, focuses attention on recent Yugoslav activity in the design of tables for astronomical navigation. The opportunity is therefore taken of adding to the review of these tables an account of S. M. Kotlaric's book; this was published in 1955 but has not previously been noticed in the Journal. English titles are used below.

It is sad to announce the death of Captain Frane Flego, after a long illness, on 21 November 1957, after this review had been written. During a brief correspondence he was able to explain one or two points about his tables in rather more detail. The authors acknowledge much assistance during correspondence with S. M. Kotlaric.